Groundwater arsenic in the Chaco-Pampean Plain,Argentina: case study from Robles county,Santiago del Estero Province |
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| Institution: | 1. School of Environmental Studies, China University of Geosciences, 430074 Wuhan, China;2. Geological Survey, China University of Geosciences, 430074 Wuhan, China;3. State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 430074 Wuhan, China;1. Cátedra de Toxicología y Química Legal, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, C1113AAD Ciudad Autónoma de Buenos Aires, Argentina;2. Dirección Nacional de Determinantes de la Salud e Investigación, Ministerio de Salud de la Nación, Av. 9 de Julio 1925, C1073ABA Ciudad Autónoma de Buenos Aires, Argentina;3. Cátedra Química Analítica I, Universidad Nacional del Chaco Austral. Cmte., Fernández 755 (3700), Pres. Roque Sáenz Peña, Chaco, Argentina;4. Grupo INQA (Investigación Química Aplicada) Facultad de Ciencias Agrarias, Universidad Nacional de Jujuy, Alberdi 47, piso 1, San Salvador de Jujuy, Jujuy CP 4600, Argentina |
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| Abstract: | In large parts of rural Argentina people depend on groundwater whose As content exceeds the Argentine drinking water standards (0.05 mg l?1). The most affected areas are located in the Chaco-Pampean Plain, where aquifers comprise Tertiary loess deposits (in the Pampean Plain) and Tertiary and Quaternary fluvial and aeolian sediments (in the Chaco Plain). Robles county is located in the alluvial cone of the Dulce River consisting of loess (aeolian), and gravel, silt, sand and clay (alluvial) deposits. In the shallow aquifers, more than 48% of the 63 studied wells show As at toxic levels (maximum 4.8 mg l?1), while in the deep groundwater the concentration is below 0.05 mg l?1. The pH of the shallow groundwaters range between 6.5 and 9 and generally have high electrical conductivity with mean values of 2072 and 1693 μS/cm?1 in the years 1998 and 1999, respectively. Arsenic concentrations are high in the alkaline Na–HCO3 type groundwaters, where As correlates positively with Na+ and HCO3?. Moreover, As correlates positively with Mo, U, and V, while a negative correlation was observed with Ca2+ and Mg2+. The potential sources of groundwater As are: (i) layers of volcanic ash with 90% of rhyolitic glass; (ii) volcanic glass dispersed in the sediments; and (iii) clastic sediments of metamorphic and igneous origin. Great lateral variability in the concentration of groundwater As is caused by several hydrogeological and hydrogeochemical factors. |
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